1. Field of the Invention
The present invention relates to a sound system in an automotive seat, and in particular to an acoustic structure of seat back provided with speakers, wherein a sound is emitted from speakers to an occupant on the seat.
2. Description of Prior Arts
There has been known an automotive seat of the type having speakers provided therein, which allows a sound, such as music, to be emitted from the speakers directly to an occupant on the seat, so that the occupant can fully enjoy the sound with both his or her ears and body. In this kind of seat, as disclosed from the Japanese Laid-Open Patent Publication No. 2002-346476, the speakers are provided behind a cushion material forming one constituent element of the seat so as to be in contact with a reverse side of the cushion material. While not taught in that literature, normally, the speakers are secured to a spring element typically provided in the seat.
The foregoing conventional acoustic structure of seat has, however, been found defective in that:
(i) the cushion material used is a foam padding material formed from urethane foam for optimal cushioning effect, but, is not suited for imparting the sound therethrough because of its property of absorbing sound and degrading acoustic effect, and
(ii) the sound emitted from each speaker is limited to a region which is substantially compassed by a diameter of the speaker itself, and such limited range of sound emission is directed to the back of an occupant on the seat, as a result of which, the occupant can not enjoy the music satisfactorily, and can not feel such vivid sound as if the music was performed in a real concert hall, neither, due to the foregoing sound absorption by the foam cushion material.
On the other hand, as known from the Japanese Laid-Open Patent Publication No 2004-97654, there is a seat having exposed speakers in its seat back to enable direct emission of sound to an occupant on the seat. According thereto, a through-bore is formed in both of foam cushion material and top cover member of the seat back and a speaker is secured in the through-bore, so that a frontal side of the speaker is exposed from the frontal surface of seat back and directly faces toward the seat occupant. However, such exposed speakers interfere with the occupant's movement, thus impairing a comfortable seating condition of the seat, and further, the range of sound emission from such exposed speaker arrangement is limited to a narrow space around the seat occupant, so that the occupant can not fully enjoy the sound or music with his or her body.